Physics, Techniques and Review of Neuroradiological Applications of Diffusion Kurtosis Imaging (DKI)

Abstract

In recent years many papers about diagnostic applications of diffusion tensor imaging (DTI) have been published. This is because DTI allows to evaluate in vivo and in a non-invasive way the process of diffusion of water molecules in biological tissues. However, the simplified description of the diffusion process assumed in DTI does not permit to completely map the complex underlying cellular components and structures, which hinder and restrict the diffusion of water molecules. These limitations can be partially overcome by means of diffusion kurtosis imaging (DKI). The aim of this paper is the description of the theory of DKI, a new topic of growing interest in radiology. DKI is a higher order diffusion model that is a straightforward extension of the DTI model. Here, we analyze the physics underlying this method, we report our MRI acquisition protocol with the preprocessing pipeline used and the DKI parametric maps obtained on a 1.5 T scanner, and we review the most relevant clinical applications of this technique in various neurological diseases.

Value of diffusion kurtosis imaging in assessing low‐grade gliomas

“…The accompanying decrease in RK in the cNAWM of LGG patients suggests microstructural disruptions to the cellular membrane or demyelination rather than axonal degeneration indicated by a nonsignificant increment of AK. 38 The relative sensitivity of diffusion and kurtosis metrics were found to be different across all comparisons made in the study. For example, FA was found to be the least sensitive in identifying changes between the lesion and cNAWM and between the pWM and cNAWM, but was found to be highly sensitive in identifying differences between the cNAWM of patients with LGGs and NCs.…”

“…The significant decrease in MK in NAWM of LGG patients, which is regarded as a sign of decreased microstructural complexity, can be attributed to increased water content due to underlying inflammation, demyelination, or axonal disorganization. The accompanying decrease in RK in the cNAWM of LGG patients suggests microstructural disruptions to the cellular membrane or demyelination rather than axonal degeneration indicated by a nonsignificant increment of AK …”

Functional MRI vs. navigated TMS to optimize M1 seed volume delineation for DTI tractography. A prospective study in patients with brain tumours adjacent to the corticospinal tract

“…However, many of these interesting advances including both MRI acquisition and tractography approaches have not yet entered clinical routine. Nonetheless, recent technical innovations such as the use of optimized b -values and kurtosis tensor strategies (Marrale et al, 2015, Lanzafame et al, 2016) may further improve the future value of diffusion imaging in routine diagnostics. Furthermore, the improving processor power of modern computers will, in time, enable probabilistic DTI tractography to be fast enough for routine clinical use in preoperative tumour diagnostics.…”

Abnormal cerebral microstructures revealed by diffusion kurtosis imaging in amyotrophic lateral sclerosis

“…First, DKI takes into account the fundamentally non‐Gaussian property of water diffusion in real and complex brain tissues, leading to better neural tissue characterization . DKI has been suggested as a promising approach to offer a more comprehensive and sensitive detection of brain tissue microstructural alterations in several pathological conditions, such as mild cognitive impairment and Alzheimer's disease, Parkinson's disease, epilepsy, and traumatic brain injury . Second, DKI allows assessment of microstructural characterization in both GM and WM simultaneously, which facilitates whole‐brain exploration of microstructural changes in various neurological disorders …”